scholarly journals Avian Influenza H7N9 Virus Adaptation to Human Hosts

Viruses ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 871
Author(s):  
Swan Tan ◽  
Muhammad Farhan Sjaugi ◽  
Siew Chinn Fong ◽  
Li Chuin Chong ◽  
Hadia Syahirah Abd Raman ◽  
...  
Keyword(s):  
Amino Acid ◽  
Avian Influenza ◽  
Human Infection ◽  
Amino Acid Substitutions ◽  
Human Adaptation ◽  
H7n9 Virus ◽  
Avian Virus ◽  
Human Viruses ◽  
Virus Adaptation ◽  
Influenza H7n9 Virus

Avian influenza virus A (H7N9), after circulating in avian hosts for decades, was identified as a human pathogen in 2013. Herein, amino acid substitutions possibly essential for human adaptation were identified by comparing the 4706 aligned overlapping nonamer position sequences (1–9, 2–10, etc.) of the reported 2014 and 2017 avian and human H7N9 datasets. The initial set of virus sequences (as of year 2014) exhibited a total of 109 avian-to-human (A2H) signature amino acid substitutions. Each represented the most prevalent substitution at a given avian virus nonamer position that was selectively adapted as the corresponding index (most prevalent sequence) of the human viruses. The majority of these avian substitutions were long-standing in the evolution of H7N9, and only 17 were first detected in 2013 as possibly essential for the initial human adaptation. Strikingly, continued evolution of the avian H7N9 virus has resulted in avian and human protein sequences that are almost identical. This rapid and continued adaptation of the avian H7N9 virus to the human host, with near identity of the avian and human viruses, is associated with increased human infection and a predicted greater risk of human-to-human transmission.

scholarly journals Early Alterations of the Receptor-Binding Properties of H1, H2, and H3 Avian Influenza Virus Hemagglutinins after Their Introduction into Mammals

2000 ◽  
Vol 74 (18) ◽  
pp. 8502-8512 ◽  
Author(s):  
Mikhail Matrosovich ◽  
Alexander Tuzikov ◽  
Nikolai Bovin ◽  
Alexandra Gambaryan ◽  
Alexander Klimov ◽  
...  
Keyword(s):  
Amino Acid ◽  
Avian Influenza ◽  
Receptor Binding ◽  
Influenza Viruses ◽  
Interspecies Transmission ◽  
Amino Acid Substitutions ◽  
Single Mutation ◽  
Binding Properties ◽  
Avian Virus ◽  
Human Viruses

ABSTRACT Interspecies transmission of influenza A viruses circulating in wild aquatic birds occasionally results in influenza outbreaks in mammals, including humans. To identify early changes in the receptor binding properties of the avian virus hemagglutinin (HA) after interspecies transmission and to determine the amino acid substitutions responsible for these alterations, we studied the HAs of the initial isolates from the human pandemics of 1957 (H2N2) and 1968 (H3N2), the European swine epizootic of 1979 (H1N1), and the seal epizootic of 1992 (H3N3), all of which were caused by the introduction of avian virus HAs into these species. The viruses were assayed for their ability to bind the synthetic sialylglycopolymers 3′SL-PAA and 6′SLN-PAA, which contained, respectively, 3′-sialyllactose (the receptor determinant preferentially recognized by avian influenza viruses) and 6′-sialyl(N-acetyllactosamine) (the receptor determinant for human viruses). Avian and seal viruses bound 6′SLN-PAA very weakly, whereas the earliest available human and swine epidemic viruses bound this polymer with a higher affinity. For the H2 and H3 strains, a single mutation, 226Q→L, increased binding to 6′SLN-PAA, while among H1 swine viruses, the 190E→D and 225G→E mutations in the HA appeared important for the increased affinity of the viruses for 6′SLN-PAA. Amino acid substitutions at positions 190 and 225 with respect to the avian virus consensus sequence are also present in H1 human viruses, including those that circulated in 1918, suggesting that substitutions at these positions are important for the generation of H1 human pandemic strains. These results show that the receptor-binding specificity of the HA is altered early after the transmission of an avian virus to humans and pigs and, therefore, may be a prerequisite for the highly effective replication and spread which characterize epidemic strains.

scholarly journals Characterization of Mouse Monoclonal Antibodies Against the HA of A(H7N9) Influenza Virus

Viruses ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 149 ◽  
Author(s):  
Mutsumi Ito ◽  
Seiya Yamayoshi ◽  
Kazushi Murakami ◽  
Kenji Saito ◽  
Atsuo Motojima ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Amino Acid ◽  
Antigenic Site ◽  
Prototype Strain ◽  
Human Infection ◽  
Antigenic Drift ◽  
Amino Acid Substitutions ◽  
H7n9 Virus ◽  
Lethal Infection

Many cases of human infection with the H7N9 virus have been detected in China since 2013. H7N9 viruses are maintained in chickens and are transmitted to humans at live bird markets. During circulation in birds, H7N9 viruses have accumulated amino acid substitutions in their hemagglutinin (HA), which resulted in an antigenically change in the recent H7N9 viruses. Here, we characterized 46 mouse monoclonal antibodies against the HA of the prototype strain. 16 H7-HA-specific monoclonal antibodies (mAbs) possessed hemagglutination inhibition (HI) and neutralization activities by recognizing the major antigenic site A; four other H7-HA-specific clones also showed HI and neutralizing activities via recognition of the major antigenic sites A and D; seven mAbs that reacted with several HA subtypes and possibly recognized the HA stem partially protected mice from lethal infection with prototype H7N9 virus; and the remaining 19 mAbs had neither HI nor neutralization activity. All human H7N9 viruses tested showed a similar neutralization sensitivity to the first group of 16 mAbs, whereas human H7N9 viruses isolated in 2016‒2017 were not neutralized by a second group of 4 mAbs. These results suggest that amino acid substitutions at the epitope of the second mAb group appear to be involved in the antigenic drift of the H7N9 viruses. Further analysis is required to fully understand the antigenic change in H7N9 viruses.

scholarly journals Genetic tuning of the novel avian influenza A(H7N9) virus during interspecies transmission, China, 2013

2014 ◽  
Vol 19 (25) ◽  
Author(s):  
D Wang ◽  
L Yang ◽  
R Gao ◽  
X Zhang ◽  
Y Tan ◽  
...  
Keyword(s):  
Amino Acid ◽  
Avian Influenza ◽  
Influenza A ◽  
Case Fatality ◽  
Host Adaptation ◽  
Human Infection ◽  
Interspecies Transmission ◽  
H7n9 Virus ◽  
Binding Preference ◽  
Genetic Tuning

A novel avian influenza A(H7N9) virus causing human infection emerged in February 2013 in China. To elucidate the mechanism of interspecies transmission, we compared the signature amino acids of avian influenza A(H7N9) viruses from human and non-human hosts and analysed the reassortants of 146 influenza A(H7N9) viruses with full genome sequences. We propose a genetic tuning procedure with continuous amino acid substitutions and reassorting that mediates host adaptation and interspecies transmission. When the early influenza A(H7N9) virus, containing ancestor haemagglutinin (HA) and neuraminidase (NA) genes similar to A/Shanghai/05 virus, circulated in waterfowl and transmitted to terrestrial poultry, it acquired an NA stalk deletion at amino acid positions 69 to 73. Then, receptor binding preference was tuned to increase the affinity to human-like receptors through HA G186V and Q226L mutations in terrestrial poultry. Additional mammalian adaptations such as PB2 E627K were selected in humans. The continual reassortation between H7N9 and H9N2 viruses resulted in multiple genotypes for further host adaptation. When we analysed a potential association of mutations and reassortants with clinical outcome, only the PB2 E627K mutation slightly increased the case fatality rate. Genetic tuning may create opportunities for further adaptation of influenza A(H7N9) and its potential to cause a pandemic.

scholarly journals Characterization of H9N2 influenza A viruses isolated from chicken products imported into Japan from China

2006 ◽  
Vol 135 (3) ◽  
pp. 386-391 ◽  
Author(s):  
M. MASE ◽  
M. ETO ◽  
K. IMAI ◽  
K. TSUKAMOTO ◽  
S. YAMAGUCHI
Keyword(s):  
Influenza Virus ◽  
Amino Acid ◽  
Avian Influenza ◽  
Avian Influenza Virus ◽  
Influenza A ◽  
H9n2 Virus ◽  
Amino Acid Substitutions ◽  
Influenza A Viruses ◽  
Potential Sources

We characterized eleven H9N2 influenza A viruses isolated from chicken products imported from China. Genetically they were classified into six distinct genotypes, including five already known genotypes and one novel genotype. This suggested that such multiple genotypes of the H9N2 virus have possibly already become widespread and endemic in China. Two isolates have amino-acid substitutions that confer resistance to amantadine in the M2 region, and this supported the evidence that this mutation might be a result of the wide application of amantadine for avian influenza treatment in China. These findings emphasize the importance of surveillance for avian influenza virus in this region, and of quarantining imported chicken products as potential sources for the introduction of influenza virus.

scholarly journals Evolution and Adaptation of the Avian H7N9 Virus into the Human Host

2020 ◽  
Vol 8 (5) ◽  
pp. 778
Author(s):  
Andrew T. Bisset ◽  
Gerard F. Hoyne
Keyword(s):  
Amino Acid ◽  
Avian Influenza ◽  
Influenza A ◽  
Amino Acid Sequences ◽  
Influenza Viruses ◽  
Amino Acid Substitutions ◽  
Upper Respiratory Tract ◽  
Viral Polymerase ◽  
Evolutionary Changes ◽  
Avian Origin

Influenza viruses arise from animal reservoirs, and have the potential to cause pandemics. In 2013, low pathogenic novel avian influenza A(H7N9) viruses emerged in China, resulting from the reassortment of avian-origin viruses. Following evolutionary changes, highly pathogenic strains of avian influenza A(H7N9) viruses emerged in late 2016. Changes in pathogenicity and virulence of H7N9 viruses have been linked to potential mutations in the viral glycoproteins hemagglutinin (HA) and neuraminidase (NA), as well as the viral polymerase basic protein 2 (PB2). Recognizing that effective viral transmission of the influenza A virus (IAV) between humans requires efficient attachment to the upper respiratory tract and replication through the viral polymerase complex, experimental evidence demonstrates the potential H7N9 has for increased binding affinity and replication, following specific amino acid substitutions in HA and PB2. Additionally, the deletion of extended amino acid sequences in the NA stalk length was shown to produce a significant increase in pathogenicity in mice. Research shows that significant changes in transmissibility, pathogenicity and virulence are possible after one or a few amino acid substitutions. This review aims to summarise key findings from that research. To date, all strains of H7N9 viruses remain restricted to avian reservoirs, with no evidence of sustained human-to-human transmission, although mutations in specific viral proteins reveal the efficacy with which these viruses could evolve into a highly virulent and infectious, human-to-human transmitted virus.

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